This proposal requests funds for an Applied Biosystems SCIEX QTRAP 5500 mass spectrometer with an Ultra 2D nano liquid chromatographic (LC) system from Eksigent, This system has been chosen specifically for the clinical/translational studies in which absolute quantification of a single or many proteins is obtained using an approach known as multiple reaction monitoring (MRM). MRM assays produce the same quality data as a ELISA but without the need for antibodies. Thus, MRM condenses the time and expense of quantitative assay development for one or more protein in clinical sample sets. Furthermore, multiplex MRM assays eliminate the need for antibody arrays, which are technically challenging and often limited. We will be using the QTRAP 5500 LC/MS/MS specifically for MRM assays in the context of large clinical cohorts where the unique aspects of this equipment are essential. Examples include situations where (i) a large number of proteins (40+), and their modified forms are assayed simultaneously, (ii) maximal sensitivity is needed for broad proteome coverage (1e7+), (iii) large sample sets (500+) must be examined and (iv) only very small quantities of irreplaceable samples are available. A group of very experienced investigators with targeted studies to address key clinical questions will use the QTRAP 5500. Seven teams constitute the major users and include researchers and MS experts from the Johns Hopkins CTSA/ITCR Biomarker Development Center directed by Jennifer Van Eyk, and the laboratories of Anne Murphy, Allen Everett and James Casella, Josef Coresh, M. Christine Zink and David Graham, Harry (Hal) Dietz as well as Gerald Hart. The researchers will work collaboratively to maximize the instrument use and to ensure high quality and effective data analysis. The projects address clinical questions in cardiology, vascular biology, stroke, diabetes, sickle cell anemia, cystic fibrosis, cancer, and HIV. Each project is poised to impact clinical medicine. PUBLIC HEALTH RELEVANCE: This proposal requests funds for a mass spectrometer capable of quantifying specific proteins in clinical samples. The unique aspects of this particular instrument is it's (i) ability to simultaneously analyze a large number of proteins and their modified forms (40+), (ii) increased sensitivity which maximizes proteome coverage (1e7+), (iii) capability to analyze large sample numbers (500+) with (iv) very small quantities of human clinical samples. The projects address important and pressing clinical questions in cardiology, vascular biology, stroke, diabetes, sickle cell anemia, cystic fibrosis, cancer, and HIV. Each project is poised to impact clinical medicine.